What should we make of the federal prosecutorial purge?

As detailed in this AP article, "the investigation into the Bush administration's firings of U.S. attorneys intensified yesterday as lawmakers ordered two more ousted officials to tell their stories, and the Justice Department said that Republican Sen. Pete V. Domenici had complained repeatedly to the attorney general about one of the prosecutors."  This related AP piece notes that "as many as six of eight former prosecutors dismissed in recent months were expected to tell House and Senate committees Tuesday that they were given little or no information about the reason for their firings." 

Currently providing lots of (partisan) coverage is Josh Marshall at TPM.  Among other interesting materials, TPM has this comment purportedly from a current federal prosecutor, writing anonymously, who views the prosecutorial purge "as part of a much larger story on the devastating impact of this administration's policies on the institution of the U.S. Attorney's Office."   All the recent developments suggest that Tuesday's Senate hearing and House hearing on the firings ought to make for good theater.  But is there any deeper story that will truly resonate? 

Though much is often made about prosecutorial independence, a certain measure of politics clearly does, and arguably always should, shape prosecutorial policies and decision-making in state and federal criminal justice systems.  There will be a Captain Renault quality to these hearings if members of Congress claim to be "shocked, shocked" to find that politics is influencing federal prosecutorial realities.